Beloitoceras plebium
Middle Ordovician
Grand Detour Formation
Rock County, Wisconsin, USA

60mm nautiloid. Rare

Beloitoceras is an extinct genus of cephalopods, specifically a type of nautiloid that lived during the Late Ordovician period, approximately 445-455 million years ago. The genus is known from fossil specimens found in North America, specifically in the states of Wisconsin and Minnesota.

Beloitoceras had a coiled, chambered shell that could reach up to 10 centimeters in diameter. The shell had a distinctive ornamentation, with prominent ribs and constrictions that gave it a segmented appearance. Like other nautiloids, Beloitoceras likely lived in shallow seas and used its tentacles to capture prey.

Beloitoceras is an important index fossil, meaning it is used by geologists to date and correlate rock formations from the Late Ordovician period. The genus is also of interest to paleontologists studying the evolution of cephalopods and the history of life on Earth.